Calibration standards are usually built to have properties similar to perfect black bodies, namely a high absorptivity and a high emissivity. Examples of how to design calibration loads can be found for example in the documents WO 2010/020816 and WO 2010/0200814 disclosing calibration loads.
In document WO 2010/020814 a calibration load is disclosed for use in calibrating an electromagnetic sensor, the calibration load comprising a multiplicity of protruding elements projecting from a surface, wherein the projecting elements are arranged with a degree of randomness, thereby suppressing Bragg reflections from the surface.
In document WO 2010/020816 a calibration load is disclosed that may be used in calibrating a radiometer, the calibration load comprising a hollow disk of thermally conductive material defining a cavity, with an aperture at the center of one face of the disk.